Adhesive bonding and miscellaneous chemical manufacture – Delaminating processes adapted for specified product – Delaminating in preparation for post processing recycling step
Patent
1991-12-13
1993-11-09
Kunemund, Robert
Adhesive bonding and miscellaneous chemical manufacture
Delaminating processes adapted for specified product
Delaminating in preparation for post processing recycling step
1566181, 1566202, 1566205, 156DIG63, C30B 1530
Patent
active
052599191
DESCRIPTION:
BRIEF SUMMARY
FIELD OF ART
This invention relates to a method of manufacturing monocrystals of oxide, and more particularly a method of manufacturing a substrate material for use in superconductor devices.
BACKGROUND ART
A phenomenon of superconduction is the most specific phenomenon among electro-magnetic characteristics manifested in substances, and development in various field of applications is greatly expected for the utilization of a perfect conductivity, a perfect diamagnetic property and quantizing of magnetic flux.
Among electronic devices utilizing superconduction phenomena are included a high speed switch, a high sensitive detecting element, a high sensitive fluxmeter and many other electronic devices.
As a superconductor which has been widely used in conventional superconductor devices, Nb.sub.3 Ge thin film formed on a substrate by using plasma sputtering technique may be mentioned. However, the critical temperature of Nb.sub.3 Ge thin film is at most 23.degree. K. Therefore, it can be used only within temperatures of liquid helium When liquid helium is used, however, cost for cooling and technological burden necessary to install a liquefying and cooling equipment of helium are increased. In addition, resource for helium is extremely limited. These problems hindered use of liquid helium in industrial field as well as for public welfare.
Various investigations have been made for obtaining superconductors having high critical temperatures. Remarkable progress has been made in recent investigations on oxide superconductor thin films. As a consequence, the critical temperature of superconductors becomes 77.degree. K. or higher. Thus, the superconductors can operate by using inexpensive liquid nitrogen as cooling medium.
In conventional methods, such oxide superconductor films have been formed on a MgO monocrystal substrate or a SrTiO.sub.3 monocrystal substrate heated to a high temperature by using sputtering or vapor deposition technique.
Among other monocrystals used as substrates, attentions have been paid to sapphire, YSZ, silicon, gallium arsenide, LIN O.sub.3, GGG, LaGaO.sub.3, LaALO.sub.3, etc.
In a conventional method of manufacturing superconductor thin films on a MgO monocrystalline substrate or a SrTiO.sub.2 monocrystalline substrate, it is impossible to stably increase the superconduction critical current (Jc). Furthermore there is a problem that the superconduction critical temperature (Tc) is not stable.
To form excellent epitaxial films, the substrate material is required to satisfy the following conditions of epitaxially growing the film. C., since the substrate material is heated to a high temperature.
As oxide superconductors having high critical temperatures, many oxides have been reported such as oxide thin films of LnBa.sub.2 Cu.sub.3 O.sub.7-x (x=0-1, Ln: Yb, Er,Y,H.sub.0, Gd, Eu, Dy) B.sub.i -Sr-Ca-Cu-O and oxide thin films of Tl-Ba-Ca-Cu-O.
The lattice constants a and b of these oxides are all included in a range of 3.76-3.92 .ANG.. By rotating the coordinate system by 45 degrees, .sqroot.2.multidot.a and .sqroot.2.multidot.b can also be deemed as fundamental lattice, in which the lattice constants a and b are expressed by 5.32-5.54 .ANG..
For magnesium oxide (MgO) presently used widely as a substrate material, a=4.203 .ANG. and the difference in the lattice constants reaches 7-11%, so that it has been extremely difficult to obtain excellent epitaxially grown films. This problem has also occurred for sapphire YSZ, silicon, gallium arsenide, LiNbO.sub.3 and GGG.
When compared with MgO, SrTiO.sub.3 has a small difference of 0.4-4% in the lattice constant from the oxide superconductor thin film as well as an excellent lattice matching property. At present, however, SrTiO.sub.3 can be prepared only by Bernoulli method, and its crystal property is very poor so that only crystals having an etch pit density of larger than 10.sup.5 /cm .sup.2 can be obtained. Accordingly, it is difficult to form an excellent epitaxially grown film on such substrate having poor crystal quality. Furthermore, i
REFERENCES:
"Physical Properties of Magnetic 2-D Oxides Containing Cr.sup.3+, (SrCaR).sub.2 (Cr.sub.x Ga.sub.1-x)O.sub.4, (R=La or Sm)," Journal of the Physical Society of Japan, vol. 44, No. 4, 1978, pp. 1083-1090.
"Key to the World's Chemical Literature," Chemical Abstracts, vol. 88, No. 26, 1978, p. 740.
Kabushiki Kaisha Komatsu Seisakusho
Kunemund Robert
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